Arsenal boss Arsene Wenger admits Shkodran Mustafi is suffering a confidence crisis.
Mustafi, 26, – dropped by Germany last month – has come under fire in recent weeks after committing errors that led to goals for Southampton, CSKA Moscow, and at Newcastle last time out.
Wenger said: “Mustafi is a young defender who has had ups and downs. But I believe overall he has potential. Yes, his confidence is lower than before. He has played many games and most of the mistakes he made have been post-Europa League games because he was a bit jaded.
“On that front that is part of the fatigue factor which would be the explanation why he had some less good games."
Wenger has no plans to take him out of the line of fire for today's clash with West Ham.
He added: “I know as a player you can forget quickly how good you are.
“You have to remind them they're not as a bad as people think of them at the moment. And that nothing is permanent. Even if you go through a spell which is a bit more difficult, you can always come out of it.
“You remind them as well that what's happening is not definite and it's just a thing that we can have an influence on."